Conventionally, an auxialiary nozzle for a loom is formed into a hollow-rod-like member by a press drawing process or by seamless welding of a metal sheet, as disclosed in Japanes Unexamined Patent Publication (Kokai) Nos. 54042/1983, 106541/1934 and the like. The following conditions should be fulfilled in terms of functional or positional restriction thereof.
First, in weft insertion, a tip portion of an auxiliary nozzle has to be moved into a warp shedding and moved backward from the warp shedding before beating up takes place. At this time, the tip portion of the auxiliary nozzle is moved into the warp shedding while forcing itself through the sheet-like warps, and therefore the outer peripheral surface thereof rubs against the warp. Therefore, a sectional width of the auxiliary nozzle has to be made as small as possible in order to avoid friction with the warp, to minimize an increase of friction and tension of the warp and to not impede jetting of air from the auxiliary nozzle for carrying weft.
The auxiliary nozzle, in a state wherein internal air stays therein, jets air for carrying weft from a small jet orifice at a predetermined flow velocity. Therefore, the larger the internal area near the jet orifice, the higher the speed of jet flow, and therefore the volume thereof should be made as large as possible. On the other hand, the length (depth) of the jet orifice need have a dimension in excess of a predetermined value in comparison to the diameter of the jet orifice in order to stabilize and straighten the direction of the jet flow. Such a theoretical elucidation is disclosed in, for example, Japanese Patent Publication (Kokoku) No. 32733/1985.
As described above, the auxiliary nozzle of this kind need be fulfilled with the reciprocal requirement in which the dimension of the outside diameter is made as small as possible and the internal volume made large, but a metal nozzle manufactured by the above-described processing method is limited in fulfilling this requirements.
Since the tip portion of the auxiliary nozzle is moved into and backward from the warp shedding while rubbing against the warp, the outer peripheral portion of the auxiliary nozzle becomes worn, and surface flaws, cracks, burrs or the like occur. If these become large, the warp becomes damaged, cut or fluffed, deteriorating the quality of the woven fabric. Therefore, the surface thereof should have an excellent wear resistance.
Japanese Unexamined Utility Model Publication (Kokai) No. 28887/1987 discloses a nozzle body which is formed of a cermet material excellent in toughness in order to improve the wear resistance of the surface. However, the inner wall surface of the jet orifice should be as smooth as possible to converge and straighten the jet flow. The roughness of the surface need be 0.5 .mu.m or less. In the normal cermet material, grains thereof are large and the cermet comprises a composition of hard grains and a metal binder. Therefore, as wear progresses, the hard grains project, as a result of which the surface and inner wall surface become rough, failing to fulfill the necessary condition of surface roughness.
Furthermore, it has an insufficient wear resistance, and it is difficult to mold a pipe-like configuration on which one end is closed. It is also very difficult to mold so as to have a one-sided wall thickness, failing to obtain a thin auxiliary nozzle.
Moreover, it is contained contemplated that a ceramics layer is formed by flame coating processing in order to improve the wear resistance, which however involves the problem of drilling a jet orifice. That is, a jet orifice for jetting air must be provided at the fore end portion of the auxiliary nozzle, but when the ceramic is subjected to flame coating processing after a jet orifice has been made in the nozzle body, an uneven layer of the ceramics layer occurs on the inner surface of the jet orifice because it is difficult to apply even flame coating to the inner peripheral surface of the jet orifice. If the inner surface of the jet orifice is uneven, the jet flow becomes unstabilized and in addition the flame coated layer on the surface of the nozzle body can possibly peel off, thus failing to provide a sufficient function as an auxiliary nozzle.
Moreover, in the manufacture of auxiliary nozzles, drilling processing is also important, which processes include electric discharge machining, diamond drilling, laser processing, supersonic vibration machining, etc. Among these processes, as a process for making a jet orifice of an auxiliary nozzle, electric discharge machining is most effective since burring of an open surface of a jet orifice and chamfering after the process need not be employed, finishing is good in terms of jet characteristics of the fluid, drilling with high accuracy becomes possible, and the drilling process is inexpensive as well as making volume production possible. As described above, it is desirable to employ a conductive material for manufacturing an auxiliary nozzle.
The auxiliary nozzle according to the present invention can be utilized for a sub-nozzle for an air jet loom within a shuttleless loom, and the method for the manufacture thereof can be utilized for manufacturing a nozzle member made of ceramics of the same kind.